Hydrocarbon continuity investigation of Sarvak and Ilam reservoirs in Azadegan oilfield using integration of geochemical, geological and reservoir engineering data

Azadegan oilfield, located in Abadan Plain, is considered as one of the largest undeveloped oilfields in Iran. The carbonate Sarvak (Middle Cretaceous) and Ilam (Upper Cretaceous) reservoirs have been completely separated by the shaly Lafan Formation in this oilfield. Here, in order to investigate the connectivity between the oils of the mentioned reservoirs, organic geochemical data were integrated with the geological and reservoir pressure information. Geochemical data show that the oils of Sarvak and Ilam reservoirs have a common genetic family, originated from a marine source rock, and their geochemical characteristics are identical. Also, they have a same thermal maturity in the range of middle oil generation window. However, two distinct and unrelated oil groups were identified in these reservoirs based on the results of C7 light hydrocarbons, confirmed by the reservoirs’ pressure data. This is due to stratigraphic situation of the thin impermeable shaly Lafan Formation related to the studied reservoirs, disconnecting the hydrocarbon connectivity between them. Based on the results obtained from this study, geochemical investigation of hydrocarbon reservoirs can be appropriately used for assessment of reservoir connectivity and would improve the reservoir models which in turn plays a crucial role in reducing the risk of the field’s development and production programs.